There is known a superconducting magnetic energy storage (SMES) that stores energy by flowing current through a coil in the superconducting state. The superconducting coil of the SMES are collectively contained in a vacuum insulating container in a factory or onsite. To achieve the superconducting state, the superconducting coils are cooled by a forced circulation cooling or immersion cooling system using liquid helium.
In recent years, it is expected to achieve larger size superconducting coil devices. In a large size superconducting coil device, coil incorporating work and final assembling work of the container are required to be implemented on site. Further, after the assembling work, work for initial cooling of the coil into a cryogenic state is performed. For these pieces of work, work on site and a lot of time are required, which causes high cost and an increase in the work period.
Also, at the time of occurrence of a malfunction, or maintenance, it is required for the entire device to be subjected to vacuum break to raise temperature, and in the case of a large size device, a long time is required before resumption of operation. Further, the number of man-hours for disassembling and assembling work on site is large. For these reasons, the device should be stopped for a long time, which may cause problems in an operational aspect of facilities.
In a superconducting coil, a magnetic circuit such as a multipole system or a toroidal arrangement system is used. In a superconducting coil device of the multipole system, a superconducting coil is cylindrically wound and layered, and further a plurality of coils are arranged, which are contained in a vacuum insulating container. The inside of the vacuum insulating container is typically cooled by liquid helium. Inside a vacuum chamber of the vacuum insulating container, a radiation shield is installed to reduce heat intrusion due to radiation from outside. The radiation shield is formed by layering material having a radiation heat reflecting surface. The liquid helium inside the container is vaporized by loss due to energizing or charging/discharging of the coils, or heat intrusion from outside. The vaporized helium is cooled and recondensed by a refrigerator provided on or outside the insulating container to return to the liquid, which is again used for cooling the coils.
On the other hand, in a superconducting coil device of the toroidal arrangement system, element coils are annularly arranged, and therefore upon energizing, inward force by its corresponding magnetic circuit acts on the coils. In order to support the inward force and self-weights of the coils, a support member for supporting them from outer diameter sides of the element coils is provided.
The superconducting coil device used for the SMES includes: a coil part that stores electrical energy in the form of the DC magnetic field; a cryostat that is a storing container for keeping the coil part at a cryogenic temperature; a refrigerator- or refrigerant-based cryogenic cooling device that is intended to bring the coil part and a current lead part into a cryogenic state; the current lead that is used for a conductive circuit for transferring electricity between a cryogenic region and a room temperature region, and the like.
In addition, in the case of the toroidal arrangement coil in which the element coils are arranged in a circumferential direction to form a circumferential direction magnetic circuit, there is required a support system for respective forces including the centrally directed inward force generated in each of the element coils by a magnetic field, attractive or repulsive force between the element coils generated due to the magnetic field unbalance between the element coils, and the self-weights of the coils.
Conventional superconducting devices have some problems as follows:
(1) In the case of employing the toroidal arrangement, the planar projection shape is a ring shape, i.e., a disc shape with a hole. When larger size devices are fabricated in future, it is required to divide the coil container and to reassemble the divided pieces on site because of dimension and weight limitations upon carriage, and assembling including attachment of coils, welding work, and airtightness test is required on site. For this reason, various disadvantages such as unsatisfactory work quality, increase in the work period, and high cost are expected.
(2) If nonconformity appears in a coil part, an internal part, or an peripheral system, there are required temperature rising, vacuum break, cut and open of the cryostat, extraction of nonconforming parts, repair in a factory or the like, reassembling of the repaired part, restoration of the cryostat, vacuuming, and cooling for achieving the superconducting state. For these works, a period of time of the order of months, and a lot of labor are required, so that it is not possible to cope with the nonconformity in a realistic way.
(3) Even in the case of a problem occurring at a single part, it is required to stop the entire device and to open the entire device to cope with the problem. Works required for the stop and reactivation should be performed for the entire device, so that the work load becomes enormous. Even in the case of the cooling work, the reservation amount of initial cooling devices should be enormous. If the amount of the initial cooling device is limited, it takes long time for the reactivation.
(4) In the toroidal arrangement, the element coils are supported from the outer diameter side; however, the outer diameter sides of the element coils have poor accuracy in shape due to winding work for wire lap winding. Because the plurality of coils are arranged in the circumferential direction, problems of breakage and characteristic deterioration due to load nonuniformity in the respective coils and among the coils are concerned. Conventionally, the support for the attractive or repulsive force between the coils generated due to the magnetic field unbalance between the element coils has not been taken into account.
In association with the above description, Japanese Patent Publication JP-A-Heisei, 10-104376A (referred to as the first conventional example) discloses a vacuum vessel for a nuclear fusion device that confines plasma and is configured by being divided into multiple sectors in a torus direction, in which dross receivers are provided along and outside multiple-divided sector division lines.
Also, Japanese Patent Publication JP2004-179550A (the second conventional example) discloses a split type cylindrical magnetic shielding apparatus including a plurality of C-shaped shaking blocks having a C-shaped cross-section and a predetermined length along an axial direction in order to form therein a magnetic shield space through a combination, wherein the C-shaped shaking block includes: a magnetic material layer formed of a magnetic material having a rectangular magnetizing characteristic and the C-shaped cross-section coupled with an internal layer and an external layer extended in the axial direction; and a coil wound at least to a part of the internal layer or the external layer of the magnetic material layer for applying a magnetic shaking current to the C-shaped shaking blocks.
Further, Japanese Patent No. 2633876 (the third conventional example) discloses a nuclear fusion device including: a hollow circular body vacuum vessel that confines plasma therein and is supported by a base through supporting legs; a plurality of superconducting toroidal field coils that surround the vacuum vessel, are arranged in a torus circumferential direction at predetermined intervals, and are respectively supported by the base through heat-insulating supporting pillars; and a heat insulating vacuum vessel that contains the superconducting toroidal field coils and the vacuum vessel, wherein each of the superconducting toroidal field coils and vacuum vessel is horizontally movably supported to the heat insulating vacuum vessel by a supporting device.